A double-hung window assembly includes a window frame and a pair of window sashes reciprocal vertically in guide rails of the master frame jamb of the window assembly. Although window sashes were traditionally made exclusively of wood, such window sashes can now be formed of extruded plastic frame members or metal frame members joined at mitred corners, for instance, to form a generally rectangular frame in which the glazing is mounted, as described in my U.S. Pat. No. 4,578,903.
U.S. Pat. No. 534,185 discloses a sash lock or fastener which, when the sash is closed, automatically locks and holds the sash in the closed position. The fastener includes a rectangular casing having an opening at its front end or faceplate in which opening a tumbler or dog is mounted, the casing being mortised into the upper sash and secured therein by screws. The tumbler is mounted within the casing by a guiding device so that the tumbler may be pivotally projected forward or longitudinally to overlie the lower sash and also to be moved laterally when projected forward to engage the casing and lock itself in position. The tumbler is biased in the projected position by a coiled, safety pin type spring mounted within the casing.
Sash security locks or fasteners similar to that disclosed in U.S. Pat. No. 534,185 are currently produced and still employ the safety pin type coil spring described hereinabove. It has been found that in the assembly of such sash locks, the coiled spring is unwieldy and difficult to properly position within the casing. Thus, these locks entail a labor expense factor in their installation attributable to the use of safety pin type springs.
The security lock embodying the invention utilizes a leaf spring which is designed to enable the lock to be assembled easily and rapidly for supply to the window manufacturer for installation. Thus, the supplier of the lock embodying the invention can provide this lock already assembled at reduced labor costs because the safety-pin type of spring is replaced.